K and M

I often see "K" used to refer to "1000" (e.g., 100K units per year).

I wonder if "M" (meaning "million") is as common as "K".
If you see, for example, "100M dollars", would you instantly know "M" refers to "million"?

Thanks

Perhaps it's not as common because people have less use for "million" than they have for "thousand". Because of its common use "K" is easily recognised as meaning "thousand".

"M" for million would not be quite as easy to recognise but still, I think, easy enough. Yeah, I'd say I'd instantly know "M" refers to million if I saw "100M dollars".

Actually, "M" is more appropriate for "million" than "K" is for thousand. Consider the origin of "K" for "thousand": it's the metric system but the true metric symbol for "thousand" is "k" not "K". "M", on the other hand, is the "million" symbol in the metric system.